Galileo, Consumed by Jupiter

Posted by jamie on Sunday September 21, 2003 @05:57AM from the faithful-servant dept.

Conceived in 1977, launched in 1989, the spacecraft Galileo ends its 34th orbit exactly one hour from now, hitting the atmosphere at 48 kilometers a second. In its long history, it taught us much, despite the failure of its main antenna that left only its tiny backup to send data, but its enduring legacy will always be the discovery that Europa's icy crust hides a planetary saltwater ocean. That ocean's potential for alien life is why the craft will self-vaporize: to avoid possible terrestrial contamination. The JPL's webcast starts roughly now, and should last about two hours (light delay). Don't miss the view from the prow and impact animations. If you're into these spacecraft and the people who build them, read Journey Beyond Selene. And while we grieve for Galileo today, remember, orbital insertion for Cassini-Huygens is only 283 days away!

We ran stories about Galileo's impending incineration earlier this month and last November when the plan was decided.

Here is a typical passage from Journey Beyond Selene, about the worst glitch in Galileo's mission, and the beginnings of how it would be worked around. Failures and the engineers who salvage them are the recurring tragic, triumphant story of our missions into space. Reproduced without permission:

With such triply redundant hardware built into their spacecraft, mission planners could feel confident that they had designed a communications system that was almost completely resistant to failure, and for the first eighteen months after Galileo's 1989 launch, there was no reason to assume anything would fail. Finally, on April 11, 1991, when the ship's trajectory had spiraled out as far as the edge of the asteroid belt between Mars and Jupiter, JPL planners decided it was at last probably safe to unlock the high-gain antenna and spread its ribs. It was only then that they'd learn if triply redundant was redundant enough.
Though the deployment of the high-gain system was not a complicated exercise, it was a critical one, and for that reason the chieftans of the Galileo project made sure they were there to watch it happen. On hand at the flight director's console that afternoon were mission director Neal Ausman, deputy mission director Matt Landanow, and project manager Bill O'Neil. O'Neil and Ausman were far and away the higher ranking of the three men, but Landanow, they all knew, was far and away the most knowledgeable. As chief engineer during the Galileo design phase, he had familiarized himself with every strut, nut and rivet of the ship, and could practically describe their placement and purpose from memory alone. If anything went wrong this afternoon, Landanow would likely be the first person to recognize it -- and the first person to come up with a way to fix it.
For the first forty minutes or so after the deployment command went up, O'Neil, Ausman and Landanow had little to do. Like so many other JPL controllers before them, they knew they would have to tolerate the nonnegotiable limits of light speed, waiting twenty minutes as their signal traveled from Pasadena to the spacecraft and then another twenty minutes as it traveled back again. For that entire time their screens told them nothing, flickering merely with the self-evident information that their command had indeed been sent. Finally, after just over the anticipated forty minutes had elapsed, a column of numbers began to blink on the glass. Landanow gave the figures a quick scan and immediately noticed something amiss. He read them again -- a bit more closely -- and this time started to feel downright queasy. The antenna, from all indications, was pulling what the engineers called stall current. The motor was drawing power, the deployment gears were engaged, but the ribs of the umbrella appeared to be going nowhere at all.
"We're stuck," Landanow said flatly.
"How can you tell?" O'Neil asked.
"The current is saturated, something is jammed," Landanow said. "In any event, the antenna's not budging."
Ausman gave the numbers on the screen a read of his own, confirmed what Landanow was saying, and immediately called out to his flight controllers, instructing them to send a second deployment command up to the ship. The engineers complied, and forty minutes later another stall signal came down. A third command yielded a third signal, and a fourth a fourth. With each new report Landanow winced. If he knew this ship -- and he surely did -- he could all but guarantee that whatever was hanging up the antenna was not much: a single too-tight fitting, perhaps, a single protruding bolt, one that was situated in just such a way that it managed to jam all eighteen ribs. If it were somehow possible to transport the Galileo spacecraft to a hangar in Pasadena, Landanow knew he could probably roll over a stepladder, climb up to the antenna, and spring it free with his hands alone. But Galileo was not in a hangar in Pasadena; it was tens of millions of miles away, at the edge of the asteroid belt between Mars and Jupiter, and more elaborate measures would be necessary.

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